1. Field of the Invention
The present invention relates to pulse detonation/deflagration actuators, engines, and other such apparatus, and related methods.
2. Description of Related Art
Conventional jet engines and the majority of rocket engines operate via subsonic combustion of fuel, known as deflagration. A pulse detonation actuator/engine is an apparatus, which in contrast, operates via supersonic detonation of fuel. Pulse detonation actuators/engines produce a high-pressure exhaust from a series of repetitive detonations within a detonation chamber. In operation, a gaseous fuel is detonated within a chamber, causing a pulse detonation wave, which propagates at supersonic speeds. The detonation wave compresses the fluid within the chamber, increasing its pressure, density and temperature. As the detonation wave passes out the open rearward end, thrust is created. The cycle is then repeated.
Pulse detonation engines conceptually allow for a high-speed cruise capability with a reliable low-cost system. Pulse detonation engines can incorporate many practical engineering advances over existing engines, such as the gas turbine. Pulse detonation allows for detonation of fuel to produce thrust more efficiently than existing systems. Pulse detonation can also be more efficient because of mechanical simplicity and thermodynamic efficiency. For example, pulse detonation engines can have fewer moving parts, lighter weight, and can require a lower cost to maintain and operate.
Application of the pulse detonation cycle requires coupling the high thermal efficiency of the detonation cycle with high propulsion efficiency in a practical device. Current combustion system models predict high propulsion efficiencies for pulse detonation engines and good thrust characteristics from low subsonic to high supersonic type regimes. Pulse detonation technology can also be applied to actuators to manipulate fluid flow, as well.
As indicated above, conventional pulse detonation/deflagration actuators and engines detonate combustible mixtures to produce thrust from high velocity exhaust gases within a high pressure and high temperature environment. The pulse detonation/deflagration actuators and engines, by their nature, however, by their nature, provide only a pulsed output. The conventional pulse detonation/deflagration actuators and engine designs generally comprise a single tube where pulsed combustion takes place at one end of the tube and travels to the other end of the tube, transforming from deflagration to detonation along the way to the end of the tube, where the highly pressurized detonation wave then exits. Methods to increase the operating frequency or magnitude of the pulsed output to try to obtain high aggregate operating frequencies and quasi-steady thrust have been generally limited to new valve techniques combined with multiple external tubes linked together and configured to perform slightly out of phase. Such additional external tubes and high-speed valves, however, not only occupy additional space and add additional weight, but they can also add an additional level of complexity. Recognized by the inventors, therefore, is need for a pulse detonation/deflagration actuator/engine or other such apparatus, which can provide for an increased operational frequency or magnitude of the pulsed output over that of the conventional pulse detonation/deflagration actuators/engines, along with a reduction in space required to operate over that of conventional applications of pulse detonation/deflagration actuators and engines.
Fluids in motion will have undesirable flow areas and areas that need directional control. One methodology of controlling fluid flow using pulse detonation devices is described, for example, in U.S. Pat. No. 6,758,032 by Hunter et al., titled “System of Pulsed Detonation Injection for Fluid Flow Control of Inlets, Nozzles, and Lift Fans,” which is incorporated herein by reference in its entirety. Hunter describes use of pulse detonation devices for controlling a nozzle jet of a jet engine. Hunter also describes the use of pulse detonation devices to simplify lift fan systems for a tactical aircraft. Further, U.S. Pub No. 2006/0254254 by Saddoughi et al. titled “Mixing-Enhancement Inserts for Pulse Detonation Chambers,” also incorporated herein by reference in its entirety, similarly describes use of pulse detonation actuators to manipulate fluid flow—particularly, thrust vectoring of a jet engine exhaust and manipulating fluid flow over aerodynamic surfaces. For thrust vectoring, the output of multiple individual pulse detonation actuators can be spaced axially along the longitudinal axis of an injection nozzle. For aerodynamic control, the output of multiple individual pulse detonation actuators can be spaced axially along the aerodynamic surface. Recognized by the inventors, however, is that, depending upon the characteristics of the flow, improved operating frequency control and/or increased pressure wave magnitude over that previously capable may be required or at least desirable to enhance system stability and reliability.